1. Field of the Invention
The invention relates to radar systems and more particularly to a radar system which includes a main transmitter and an auxiliary transmitter with the auxiliary transmitter transmitting a signal which obscures the characteristics of the main radar transmitter.
2. Description of the Prior Art
Jamming techniques are more effective if the characteristics of the radar to be jammed are known. Information relative to the characteristics of the conventional radar system may be obtained using a receiver positioned in either the main beam or in the sidelobes.
Prior art radar systems have typically used one of several techniques to reduce the susceptibility to jamming. These include frequency diversity with pseudorandom frequency selection techniques. Low sidelobe antennas were also used to narrow the beamwidth and make it more difficult to receive sufficient energy in the sidelobes to detect the radar signal and determine its transmission characteristics. Another suggested technique has been to utilize an antenna array and adapt the beam pattern so that the jamming transmitter was positioned in a null of the array. All of these systems utilize some modification of the main radar beam as a technique to make it more resistant to jamming. By contrast, the present system utilizes an auxiliary signal to obscure the sidelobes to make it difficult for a potential jammer to determine the characteristics of the radar. As a result, effective jamming requires that the jamming signal be spread over the entire possible frequency spectrum of the radar system to be jammed in order to be sure that the jamming signal includes the instantaneous spectrum of the radar transmitter.